Various types of optical displays are commonly used in a wide variety of applications including computer displays, televisions, cockpit avionics, night vision (NVIS) applications and the like. Included among these various types of optical displays are liquid crystal displays (LCDs) such as active matrix LCDs (AMLCDs). LCDs typically use a passive or active matrix display grid to form an image on the display surface. Such displays typically include any number of pixels on the display grid that are arrayed in front of a backlight. By controlling the light passing from the backlight through each pixel, color or monochrome images can be produced in a manner that is relatively efficient in terms of physical space and electrical power consumption.
Frequently, LCD backlights are implemented with fluorescent lamps or the like. A fluorescent lamp is any light source in which a fluorescent material transforms ultraviolet or other energy into visible light. Typically, a fluorescent lamp includes a glass tube that is filled with argon or other inert gas, along with mercury vapor or the like. When an electrical current is provided to the contents of the tube, the resulting arc causes the mercury gas within the tube to emit ultraviolet radiation, which in turn excites phosphors located inside the lamp wall to produce visible light. Fluorescent lamps have provided lighting for numerous home, business and industrial settings for many years.
Despite the widespread adoption of displays and other products that incorporate fluorescent light sources, however, designers continually aspire to improve the electrical efficiency of the light source, to extend the dimmable range of the light source, and/or to otherwise enhance the performance of the light source, as well as the overall performance of the display. In the avionics arena, in particular, there is a need to reduce power consumption while also improving the displayed image presented to the viewer across a wide range of luminance. Therefore, it is desirable to create an improved lamp driver system that provides a relatively wide luminance range and relatively precise brightness control while providing good electrical efficiency.